INTEGRATION OF OFFSHORE WIND FARMS TO THE GREEK TRANSMISSION SYSTEM VIA AN ISLAND INTERCONNECTION GRID

1. INTEGRATION OF OFFSHORE WIND FARMS TO THE GREEK TRANSMISSION SYSTEM VIA AN ISLAND INTERCONNECTION GRID A. Koronides J. Kabouris M. Efstathiou M. Tsili Hellenic TSO M. Papadopoulos Em. Prof. of NTUAPresident of the Hellenic TSO

2. INTRODUCTION (1) • Existing submarine cable interconnections: - AC 150kV: All Ionian islands (1964 – 76) - AC 15 – 20kV: About 65 islands (since 1960) - DC 500kV: Greece – Italy (2002) • Under construction: Cycladic Interconnection • Planned island interconnection of all the Aegean islands, in order to: (a) Eliminate the existing oil powered stations (b) Exploit the excellent wind potential

3. DEVELOPMENT STAGES • Threemain stages: (A) Preliminary planning of the “Aegean sea grid”, based on existing projections (island loads and proposals for RES installations) (B) Detailed design of the interconnection of each group of islands, to accommodate the RES plants with installation licenses (C) Construction of each interconnection, when the proper conditions (economic feasibility, technical maturity etc) are obtained.

4. ISLAND GROUPS and expected wind power • Four main interconnections – island groups and expected wind capacity (on the islands): (1) Cycladic islands (construction stage) Production licenses: 650MW (2) North Aegean islands Production licenses: 700MW (3) Crete Production licenses: 2.200MW (4) Dodecanese Expected wind power on the islands: 700MW • Stand-alone interconnection – Skyros with expected wind power 333MW

5. Applications for offshore wind farms

6. GRID INTERCONNECTION • EHV Substations (400/150 kV) have been chosen as connection points to the mainland grid • Robust system nodes (high short-circuit power) • Enough transmission capacity to absorb large wind power capacity • Limitations to the absorbed wind power • Transmission system reinforcements for the accommodation of wind power • Restrictions in the total installed wind capacity due to the transfer capacity limits between North and South Greece

7. WIND POWER PENETRATION LIMITS • of EHV Substations (400/150kV) of the mainland grid

8. AEGEAN ISLANDS PROPOSED INTERCONNECTION SCHEME

9. AEGEAN ISLANDS PROPOSED INTERCONNECTION SCHEMES • Accommodation of onshore wind farms (4583MW)

10. AEGEAN ISLANDS PROPOSED INTERCONNECTION SCHEMES • Accommodation of offshore wind farms

11. Grid Interconnection Issues • Connection of the offshore parks in islandsAlexandroupoli – Samothraki – Limnos- Agios Efstratios must be further investigated – reduction of the installed capacity of onshore parks in the North Aegean islands or Thrace • The possibility to accommodate the above offshore wind farms by connection to EHV substations (400/150 kV) of the South system is limited due to the overall onshore installed capacities in Cyclades/Dodecanese • The offshore wind farms in Karpathos can be accommodated by the interconnection of Dodecanese islands to the mainland grid • The connection of offshore wind farms in Petalioi must be investigated due to the overall onshore installed capacities in Cyclades/Dodecanese that are connected to 400/150 kV of the South system (Aharnes/Pallini) • No special considerations for the connection of offshore wind farms in the rest of the considered islands

12. Conclusions • There are possibilities of integration of offshore wind farms to the greek transmission system via an island interconnection grid in order to support Maritime Spatial Planning • The potential from offshore parks that can be accommodated by the existing or planned submarine cable interconnections is highly dependent on the onshore wind farm developments (mainland/islands) • Limitations to the absorbed wind power in the mainland grid imposed by the transmission system infrastructure should be considered